The growth of the coal industry has been arrested in part by the expectancy that nuclear fuels would prove to be cleaner and much more economical. This circumstance has failed to materialize, with nuclear power today furnishing only a mere fraction of the energy derived from coal. However, the critical demand for escalating levels of power is presently confronted with strenuous environmental objections to the liquid metal fast breeder reactor believed to be the answer to the energy impasse while the burning of coal by the electric utility companies remains stymied in the face of stringent emission codes imposed.
To further exacerbate the grim energy outlook, the exhaustion of the much more limited reserves of oil and natural gas is threatened. Against this background, coal looms as the only realistic way out of a most frustrating position if only it could be burned without attendant pollution hazards and/or practical gasification-liquification actually achieved. In brief, the vast stores of coal could insure a reasonable abundance of energy for centuries to allow sufficient time for the advent of revolutionary developments such as the controlled release of thermonuclear energy, perhaps in the form of laser-induced fusion.
Emergency measures have been taken to exert an effort to find ways of purging coal of its objectionable impurities, largely sulfur and the ash residue. In this age of intense overspecialization, it is not entirely strange that virtually an entire realm of well-established technology that had already addressed itself rather successfully to this problem in a different context has been overlooked.
The Iron and Steel Industry, over the course of many years, came to grips with the challenge of producing high quality ferrous metals and alloys, not least of which was the control of impurities. The blast furnace represents a remarkable means to manufacture voluminous amounts of raw pig iron relatively uncontaminated by a host of foreign substances contained in ore, limestone and coke, constituting the starting materials. The smelting process performed in the blast furnace restrains the entry of undesired impurities into the molten pig iron; the chemistry is tailored to purge such components as sulfur and ash as they are taken up principally by the slag. Subsequent refinement of the pig iron gives rise to high quality steel products.
The practical economics of blast furnace operations spurred the refinement of the gaseous byproducts for the recovery of fine particulates (dust) to be recycled and the manufacture of a clean gaseous fuel for heating of the air blast and for power generation for diverse ancillary purposes not least of which is the driving of compressors.
Viewed from such a vantage point, the clean use of coal has a tradition to turn to but with the provision to institute meaningful changes where prudent. Thus, the present invention, while based upon blast furnace technology, embodies several innovations which will help the coal industry which has tended to stagnate over recent years.
It is well known in the blast furnace art to introduce oxygen and/or steam with the air blast or as a substitute for the air blast to provide an enriched blast furnace gas. If the steam is introduced at the lower tuyere level water gas will be produced as a result of the standard steam-coke reaction. If steam is introduced in the upper levels of the furnace it will react with the nascent iron to produce H.sub.2.
It is also well known in the steel making art to blow oxygen through molten pig iron in the basic oxygen furnace to remove the carbon from the pig iron.